This is confusing because Bob Marvel started making conversions for Marvel Precision--they have a rib that only fits Marvel Precision conversions.Then Bob was working with Advantage Arms--they have 2 different rails depending on the vintage of the "Advantage Arms--Bob Marvel" conversion. The Advantage Arms rails don't work with the Marvel Precision.Then Bob was working with Nelson--I'm not sure about the interchangability of the Nelson rail versus the other 2 brands.

So when you say it's a Marvel conversion, that isn't the last word on the subject.

You will know you have a Marvel Precision because they engrave "Marvel 1911 - .22" on the slide. The other makers have their branding printed on the side of the slide.